A use mode of a taphole mix will be described by taking an operation of a blast furnace as an example. After completion of tapping, the taphole mix is pressingly inserted into and filled in a taphole to plug the taphole. When a time for next tapping using the taphole has come, the taphole mix burned by heat of the furnace during a preceding process is drilled to form a molten metal passage. Molten pig iron and molten slag within the furnace are discharged outside the furnace through the molten metal passage. In order to suppress a progressive increase in bore diameter of the molten metal passage during tapping so as to achieve stable tapping for a long time, the taphole mix is required to have excellent erosion/corrosion resistance to molten pig iron and molten slag.
Heretofore, it has been known that it is effective to add a silicon nitride-based material and a carbon-based (carbonaceous) material to a taphole mix in order to improve erosion/corrosion resistance of a taphole mix, as disclosed in the following Patent Document 1.
The Patent Document 1 describes that, when a taphole mix contains a silicon nitride-based material and a carbon-based material, an SiC bond is formed at about 1400° C. or more according to the following reaction formulas (1) and (2). The SiC bond densifies a matrix of the taphole mix and strengthens the matrix to improve erosion/corrosion resistance of the taphole mix.Si3N4→3Si+2N2  (1)Si+C→SiC  (2)
Specifically, the Patent Document 1 discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 75 μm or less, as a silicon nitride-based material; coke having a particle diameter of 0.3 mm or less, and pitch pellets, as a carbon-based material; and roseki having a particle diameter of 0.3 mm or less, on condition that a total amount of 100 mass % of the three components consists of about 42 mass % of the silicon nitride-based material, about 26 mass % of the carbon-based material, and about 32 mass % of the roseki (see Inventive Example 1 and paragraph [0025] in the Patent Document 1).
Besides the above taphole mix, there have also been known the following taphole mixes as the type containing a silicon nitride-based material and a carbon-based material.
The following Patent Document 2 discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 74 μm or less; carbon black having a particle diameter of less than 1 μm; and microsilica having a particle diameter of less than 1 μm, on condition that a total amount of 100 mass % of the three components consists of about 42.8 mass % of the ferro silicon nitride, about 28.5 mass % of the carbon black, and about 28.5 mass % of the microsilica (see Inventive Example 3 in the Patent Document 2).
The Patent Document 2 also discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 74 μm or less; carbon black having a particle diameter of less than 1 μm; and microsilica having a particle diameter of less than 1 μm, and clay, as a silica-based (siliceous) material, on condition that a total amount of 100 mass % of the three components consists of about 43 mass % of the ferro silicon nitride, about 14 mass % of the carbon black, and about 43 mass % of the silica-based material (see Comparative Example 1-5 in the Patent Document 2).
The following Patent Document 3 discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 0.5 mm or less; coke having a particle diameter of 2 mm or less; and an ultrafine roseki powder having an average particle diameter of 4 μm, on condition that a total amount of 100 mass % of the three components consists of 40 mass % of the ferro silicon nitride, 40 mass % of the coke, and 20 mass % of the ultrafine roseki powder (see Inventive Example 4 in the Patent Document 3).
The following Patent Document 4 discloses a taphole mix comprising: ferro silicon nitride controlled to have a particle size of 200 mesh or less, i.e., a particle diameter of about 75 μm or less; graphite controlled to have a particle size of 200 mesh or less; and roseki having a particle diameter of 0.1 mm or less, on condition that a total amount of 100 mass % of the three components consists of 50 mass % of the ferro silicon nitride, 17 mass % of the graphite, and 33.5 mass % of the roseki (see Inventive Example D in the Patent Document 4).
The following Patent Document 5 discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 45 μm or less; carbon black; and roseki having a particle diameter of 0.1 mm or less, on condition that a total amount of 100 mass % of the three components consists of 55.5 mass % of the ferro silicon nitride, 11.1 mass % of the carbon black, and 33.3 mass % of the roseki (see Inventive Examples 1 to 3 in the Patent Document 5).
The following Patent Document 6 discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 0.1 mm or less; carbon black; and roseki having a particle diameter of 0.1 mm or less, on condition that a total amount of 100 mass % of the three components consists of 71.4 mass % of the ferro silicon nitride, 4 mass % of the carbon black, and 23.8 mass % of the roseki (see Comparative Examples 3 to 7 in the Patent Document 6).
The following Patent Document 7 discloses a taphole mix comprising: ferro silicon nitride having a particle diameter of 75 μm or less; carbon black; and roseki having a particle diameter of 0.1 mm or less, on condition that a total amount of 100 mass % of the three components consists of 50 mass % of the ferro silicon nitride, 27.8 mass % of the carbon black, and 22.2 mass % of the roseki (see Sample No. 7 in Table 1 in the Patent Document 7).
[Patent Document 1]JP 2831311B[Patent Document 2]JP 2002-60820A[Patent Document 3]JP 2000-319711A[Patent Document 4]JP 08-231278A[Patent Document 5]JP 2004-10379A[Patent Document 6]JP 2001-335374A[Patent Document 7]JP 11-199337A